Immunoassay is in many cases the method of choice for detecting infection by microorganisms. As an aid to specific diagnosis, the assay must be capable of identifying a particular species of microorganism with a high degree of reliability. In most cases this requires the isolation of species specific antigens for reaction with appropriate antibodies. Typical of the type of organism yielding to such analysis is Chlamydia trachomatis, which is one of the two microorganism species of the genus Chlamydiaceae, order Chlamydiales. The other species is Chlamydia psittaci. Chlamydia trachomatis, in its some fifty various strains, are the etiologic agents for a number of human ocular and genital diseases including trachoma, inclusion conjunctivitis, lymphogranuloma venereum, "nonspecific" or nongonococcal urethritis and proctitis. C. trachomatis infection is pervasive throughout the general population. It has been estimated, for instance, that C. trachomatis is accountable for several million cases per year of nongonococcal urethritis.
Since C. trachomatis mediated disease is widespread, a reliable, simple and inexpensive test for the organism's presence is highly desirable and of great importance in order that proper treatment can be undertaken. The only serological test in current use is the microimmunofluorescence test. This test however requires that the strains of C. trachomatis be used as serological test antigen. In addition, the facilities for conducting this test are available in only a limited number of laboratories throughout the world. The test is very laborious, time consuming and difficult to perform.
Recently, U.S. Pat. No. 4,118,469, noted the preparation of an antigen of C. trachomatis useful in serological testing for lymphogranuloma venereum and nongonococcal urethritis. Such antigen was purified from C. trachomatis organisms by immunoadsorption chromatography using the monospecific antiserum as a specific ligand covalently bound in an agarose gel column. This antigen had a molecular weight of only about 160,000 daltons, and in counter-immunoelectrophoresis testing was capable of detecting antibodies from the sera of lymphogranuloma venereum patients. However, when utilized in a similar test with sera of nongonococcal urethritis patients, this antigen failed to detect antibodies. It was successful, however, in detecting antibodies in two dimensional immunoelectrophoresis testing.
In any event, however, there is still great medical interest in the isolation of species specific antigens of microorganisms, such as C. trachomatis, which are capable of detecting infection, preferably by commonly practiced antigen-antibody assay methods. It therefore is an object of the present invention to provide an improved method of isolating such species specific antigens.